Cylinder with a built-in stroke sensor having an eccentric member

ABSTRACT

A cylinder with a built-in stroke sensor which is mounted in a machine or apparatus such as a construction machine used in a severe environment, and which is designed so as to minimize the stroke sensor accommodation space and to make inspection and replacement of the stroke sensor rod easier. An eccentric member is attached to an end of a sensor rod, a recess/projection coaxial with the sensor rod is provided at the center of this member, a projection/recess axially supported by a recess/projection provided at the center of an end surface of the a head is provided at an end of this member, and a ring-like member engaging with the recess/projection of the eccentric member is mounted in the cavity of the piston rod. The arrangement may alternatively be such that a projection/recess axially supported by a recess/projection provided at the center of an end surface of a bottom is provided at an end of the eccentric member, and that a ring-like member engaging with the recess/projection of the eccentric member is mounted in the cavity of the cylinder.

TECHNICAL FIELD

This invention relates to a cylinder with a built-in stroke sensor. Moreparticularly, the invention relates to a cylinder with a built-in strokesensor mounted in a machine or apparatus such as a construction machineused in a severe environment.

BACKGROUND ART

Various working machine control devices have been proposed for thepurpose of making the operations of construction machines or the likeeasier and to reduce burdens on operators. As one of such devices, ahydraulic cylinder has been proposed which is used for each section of aworking machine, whose operating stroke is detected, and to which ahydraulic cylinder operating stroke sensor is attached. This hydrauliccylinder includes a type having a built in stroke sensor provided in itscentral portion to be protected from earth, sand, muddy water and thelike.

FIGS. 7 and 8 are cross-sectional views of head portions of cylinderswith built-in stroke sensors in accordance with the prior art wherein asensor accommodation tube 7 is provided in a cavity provided at thebottom of a fluid pressure cylinder and at the center of a piston rod 2,and wherein a stroke sensor using a potentiometer or the like isprovided in the sensor accommodation tube 7.

The stroke sensor is composed of a sensor body 5 having a resistor, anda sensor rod 6 having a brush which slides on the surface of theresistor. An end of the sensor body 5 is supported on the unillustratedbottom, and an end of the sensor rod 6 is attached by screwing with nuts14 and 15 to a plate 24 fitted to the piston rod 2 at an end of thecavity thereof. A rod head 3 is fixed to an end of the piston rod 2.

As fluid pressure is produced for action in the cylinder 1 so that thepiston rod 2 is moved reciprocatively, the sensor rod 6 of the strokesensor is also moved with the movement of the piston rod 2, the brushsliding on the resistor electrically detects a voltage value of theresistor, and this value is supplied to a controller through an electricwiring.

If a rotary motion of the piston rod 2 in a circumferential direction isallowed as well as the axial reciprocating motion when this fluidpressure cylinder is operated, a structure is required in which thestroke sensor is attached while the sensor rod 6 is made concentric withthe piston rod 2, and in which the sensor rod 6 is freely rotatablerelative to the brush. To reduce the outside diameter of the sensor body5a, it is necessary to make the the sensor rod 6 eccentric to the sensorbody 5a and to limit the direction in which the brush faces to onedirection.

In the case of the stroke sensor used as shown in FIG. 7 where thecenter of the sensor body 5 and the center of the sensor rod 6 coincidewith each other, the outside diameter of the sensor body 5 is large incomparison with the stroke sensor shown in FIG. 8 in which the sensorrod 6 is eccentric to the sensor body 5a. In the case of the strokesensor shown in FIG. 8, where the sensor rod 6 is eccentric to thesensor body 5a, the outside diameter of the sensor body 5a is reducedbut it is necessary to select a large inside diameter of the sensoraccommodation tube 7 as in the case of FIG. 7 because it is necessarythat the center of the piston rod 2 and the center of the sensor rod 6coincide with each other. Consequently, in either case of FIGS. 7 and 8,the arrangement is disadvantageous in that the stroke sensoraccommodation space is increased so that the size of the fluid pressurecylinder is large and so that the manufacture cost is high. It is alsodisadvantageous in that the operating oil for the reciprocating motionof the piston rod 2 is spattered on the sensor at the time of inspectionor replacement of the sensor body 5, and that since the cylinder bottomof the conventional type cylinders is of an integral type, the operationfor inspection or replacement of the stroke sensor is laborious andentails a leak of the operating oil.

In consideration of these problems, it is an object of the presentinvention to provide a cylinder with a built-in stroke sensor which hasa structure such that the stroke sensor accommodation space can beminimized, and whose stroke sensor can be inspected or replaced easily.

DISCLOSURE OF INVENTION

A fluid pressure cylinder with a built-in stroke sensor in accordancewith the present invention includes a cylinder having a bottom at itsone end, a tubular piston rod reciprocatively movable in the cylinderand having a rod head at its one end, and the stroke sensor constitutedby a sensor body and a sensor rod and provided in the cavity of thepiston rod, wherein an eccentric member is attached to an end of thesensor rod, a recess/projection coaxial with the sensor rod is providedat the center of this member, a projection/recess axially supported by arecess/projection provided at the center of an end surface of the rodhead is provided at an end of this member, and a ring-like memberengaging with the recess/projection of the eccentric member is mountedin the cavity of the piston rod.

The arrangement may alternatively be such that a projection/recessaxially supported by a recess/projection provided at the center of anend surface of the bottom is provided at an end of the eccentric member,and that a ring like member engaging with the recess/projection of theeccentric member is mounted in the cavity of the cylinder.

Further, a seal for preventing an operating fluid for reciprocativelymoving the piston rod from being spattered on the sensor body 5 isprovided between an inner end portion of the cylinder and an inner endportion of the piston rod.

In accordance with this arrangement, the ring-like member engaging withthe recess/projection of the eccentric member restrains the sensor rodof the stroke sensor so as to inhibit an axial movement of the samedifferent from the movement of the piston rod. Accordingly, in a casewhere the sensor rod is engaged and held on the piston rod side, as thepiston rod is reciprocatively moved while rotating, the ring-like memberslides on the eccentric member while engaging with the same, the strokesensor is not rotated, and the stroke of the reciprocating movement ofthe piston rod can be detected.

In a case where the sensor rod is engaged and held on the cylinderbottom side, as the piston rod is reciprocatively moved while rotating,the stroke sensor simultaneously extends or retracts and rotates, andthe eccentric member slides on the ring-like member while engaging withthe same, no excessive force being applied to the stroke sensor, thestroke sensor is not rotated. The stroke of the reciprocating movementof the piston rod can be detected.

In either case, the stroke sensor accommodation space can be remarkablyreduced as compared with the prior art.

Further, the operating fluid is not spattered on the sensor body sincethe seal is provided, and the stroke sensor can easily be inspected orreplaced because the cylinder bottom is designed as a separable type. Atthe time of inspection of replacement, there is no risk of the operatingfluid leaking out.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 to 4 are cross-sectional views of head portions of cylinderswith built-in stroke sensors in accordance with first to fourthembodiments of the present invention;

FIG. 5 is a cross-sectional view of a bottom portion of a cylinder witha built-in stroke sensor in accordance with a fifth embodiment of thepresent invention;

FIG. 6(a) and 6(b) are cross-sectional views of a cylinder with abuilt-in stroke sensor in accordance with a sixth embodiment of thepresent invention;

FIG. 6(a) is a front sectional view;

FIG. 6(b) is a cross-sectional view taken along the line A--A of FIG.6(a);

FIGS. 7 and 8 are cross-sectional views of head portions of cylinderswith built-in stroke sensors in accordance with the prior art;

FIG. 7 shows a cylinder with a built-in stroke sensor in which a sensorbody and a sensor rod are disposed coaxially; and

FIG. 8 shows a cylinder with a built-in stroke sensor in which a sensorrod is eccentric to a sensor body.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of cylinders with built-in stroke sensors in accordance withthe present invention will be described below in detail with referenceto the accompanying drawings.

FIGS. 1 to 4 are cross-sectional views of head portions of fluidpressure cylinders. Referring to FIG. 1, a piston rod 2 movedreciprocatively in a cylinder 1 has a tubular form, and a boss portionof a rod head 3a and a ring-like member 4a are fitted in the cavity atone end thereof and are connected to the piston rod 2. A stroke sensorhaving sensor rod 6 eccentric to a sensor body 5a is placed togetherwith a sensor accommodation tube 7a in the cavity of the piston rod 2.

An eccentric member 8a is fixed to an extreme end of the sensor rod 6.The eccentric member 8a has a projection 9a provided at its extreme end,and a groove 10a provided at its center, the groove 10a being coaxialwith the sensor rod 6. The projection 9a has an eccentricity to thecenter of the eccentric member 8a. This eccentricity is equal to thatbetween the sensor body 5a and the sensor rod 6. The projection 9a isrotatably fitted in a recess 13a formed in an end surface of the bossportion of the rod head 3a. The ring-like member 4a is partially engagedwith the groove 10a of the eccentric member 8a, and gaps for enablingsmooth sliding are formed between two side surfaces of the ring-likemember 4a and two side surfaces of the groove 10a.

As fluid pressure is produced for action in the cylinder 1 so that thepiston rod 2 is forced in or out while rotating, the ring like member 4ais maintained in the state of engaging with the eccentric member 8awhile sliding on the side surfaces of the groove 10a of the eccentricmember 8a. The sensor rod 6 therefore moves in the axial direction aloneby following the reciprocating motion of the piston rod 2 withoutrotating although the piston rod 2 is rotated, thereby detecting thecylinder stroke.

FIG. 2 shows the second embodiment of the present invention in which aprojection 13b is provided on an end surface of a boss portion of a rodhead 3b at the center thereof and is rotatably fitted in a recess 9bformed in an end surface of an eccentric member 8b. The recess 9b has aneccentricity to the center of the eccentric member 8b. This eccentricityis equal to that between the sensor body 5a and the sensor rod 6. Aring-like member 4b is partially engaged with a groove 10b having a-shaped cross sectional configuration and formed on the eccentric member8b at the center, and gaps for enabling smooth sliding are formedbetween engaging surfaces of the ring-like member 4b and two sidesurfaces of the groove 10b.

FIG. 3 shows the third embodiment of the present invention in which aneccentric member 8c has a projection 9c provided at its extreme end, anda flange 11c provided at its center. The projection 9c has aneccentricity to the center of the eccentric member 8c. This eccentricityis equal to that between the sensor body 5a and the sensor rod 6. Theprojection 9c is rotatably fitted in a recess 3c formed in an endsurface of the rod head 3c at the center thereof. A groove 10c partiallyengaged with the flange 11c of the eccentric member 8c is provided inthe ringlike member 4c at the center.

FIG. 4 shows the fourth embodiment of the present invention in which aprojection 13d is provided on an end surface of a boss portion of a rodhead 3d at the center thereof and is rotatably fitted in a recess 9dformed in an end surface of an eccentric member 8d and having aneccentricity to the center of the eccentric member 8d. This eccentricityis equal to that between the sensor body 5a and the sensor rod 6. Aflange 11d is provided on the eccentric member 8d at the center, and agroove 10d partially engaged with the flange 11d of the eccentric member8d is provided in the ring-like member 4d at the center.

The interrelation between the eccentric member 8b-d and the ring-likemember 4b-d during the reciprocating motion of the piston rod in thesecond to fourth embodiments is the same as the first embodiment, thedescription for it will not be repeated.

FIG. 5 shows a fifth embodiment of the present invention, showing astate in which an end of the sensor rod 6 of the stroke sensor isengaged at a bottom 12 of the fluid pressure cylinder. A projection 9cof an eccentric member 8e, fixed to the end of the sensor rod 6, isrotatably fitted in a recess 12a formed at the center of the bottom 12.The projection 9e has an eccentricity to the center of the eccentricmember 8e. This eccentricity is equal to that between the sensor body 5aand the sensor rod 6. A ring-like member 4e is pinched between thebottom 12 and the cylinder 1 and is partially engaged with a groove 10cof the eccentric member 8e, and gaps for enabling smooth sliding areformed between engagement surfaces of the ring-like member 4e and twoside surfaces of the groove 10e.

As fluid pressure is produced for action in the cylinder 1 so that thepiston rod 2 is forced in or out while rotating, the stroke sensorhaving the end of the sensor body 5a fixed to the piston rod 2 is alsorotated. At this time, the sensor rod 6 is rotated together with thesensor body 5a, and the eccentric member 8e has side surface portions ofits groove 10 sliding on the side surfaces of the ring-like member 4ewhile being maintained in the state of engaging with the ring-likemember 4e. Thus the stroke sensor moves in accordance with the motion ofthe piston rod 2, i.e., the reciprocating motion and the rotary motion,thereby detecting the cylinder stroke.

With respect to this embodiment, only an example of the engagement ofthe extreme end of the sensor rod 6 on the bottom 12 side of the fluidpressure cylinder (the inverse of the structure of the first embodimentshown in FIG. 1) has been explained. However, this is not exclusive, andother structures may also be adopted in which, as in the case of theexamples shown in FIGS. 2 to 4, a recess formed at an end of aneccentric member is rotatably fitted to a projection formed at thecenter of a bottom, while a flange provided at the center of theeccentric member is partially engaged with a central groove of aring-like member.

FIG. 6(a) and 6(b) show a sixth embodiment of the present invention inwhich a cylinder 1 is secured by a bottom 12b and bolts. A piston 19a isinserted in a piston rod 2 in the cylinder 1 and is fixed with nuts 19b.A packing 19c and a wear ring 19d are provided on the piston 19a, andthe piston 19a is slidably fitted in the cylinder 1. The piston rod 2is, on the rod head 3f side, loosely fitted in a sleeve fitted in aflange 16 fixed to the cylinder 1. A seal 1c is provided in a positionas between an inside diameter of the piston rod 2 and an outsidediameter of a tube 1a provided in the cylinder 1 to prevent theoperating fluid from spattering on a sensor body 5a disposed in the tube1a.

A sensor rod 6 at one end of the sensor body 5a constituted by apotentiometer or the like is engaged with and held by a pin 2b on aninner end portion of the piston rod 2, and a sensor accommodation tube7a at the other end is engaged with and held by a pin 12d on an innerend portion 12c of the bottom 12 through a sleeve 14 having aneccentricity (e). The sleeve 14 is fixed on the bottom 12 by a fixingbolt 14a such as a screw after adjustment of the zero point of thesensor body 5a.

A wiring 15 is connected to the sensor accommodation tube 7a and is ledto the outside through a hole 23 in the bottom 12.

Operating fluid supply/exhaust ports 17, 18 are formed in the cylinder1.

The cylinder 1 is attached to an unillustrated construction machine orthe like through a pin hole 20 formed in the bottom 12b and a pin hole21 formed at one end of the piston rod 2.

When, in this arrangement, the operating fluid flows in through thesupply/exhaust port 18, it forces out the piston 19a so that the pistonrod 2 extends in the direction Z of FIG. 6(a). With this extension thesensor rod 6 connected by the pin 2b also extends. With this extensionthe voltage value of the sensor accommodation tube 7a electricallyconnected through the sensor body 5a is electrically detected to measurethe length of the extension of the piston rod 2.

At this time, air flows into or out of the interior (P) of the bottom12b through the hole 23. A supply/exhaust valve may be providedseparately to enable air to flow in or out. If the variation in thecapacity of the interior (P) is small or if there is a risk of an inflowof earth and sand or rain water, air supply/exhaust may be inhibited.

The adjustment of the sensor body 5a can also be effected by rotatingthe eccentric sleeve 14, and it is also possible to fix thepotentiometer by a reamer with a structure similar to that of the pin2b, to record voltages in a memory with respect to the state where thepiston rod 2 is extended and the state where the piston rod 2 is fullycontracted, and to effect linear interpolation therebetween at the timeof measurement.

A potentiometer was used for the sensor body 5a, but it is not exclusiveand other position detectors capable of detecting the absolutedisplacement may be used.

According to the present invention, as described above, theexpansion/contraction motion of the stroke sensor can be effected withaccuracy in accordance with the reciprocating motion of the piston rod2. Also, the stroke sensor accommodation space can be minimized withrespect to the rotation of the piston rod 2 irrespective of whether thestroke sensor is maintained in a stationary state or is smoothly rotatedwith the piston rod 2, thereby preventing the increase in the size ofthe fluid pressure cylinder and the increase in manufacture cost. It isalso possible to improve the compatibility with fluid pressure cylindershaving no built-in stroke sensor.

Further, there is no risk of the operating fluid leaking out at the timeof inspection or replacement of the stroke sensor, and the facility withwhich inspection or replacement is effected is improved.

Industrial Applicability

The present invention is suitable for a cylinder with a built-in strokesensor mounted in a construction machine or apparatus such as aconstruction machine used in a severe environment, and is particularlyuseful as a cylinder with a built-in stroke sensor in which the strokesensor accommodation space is small and which is improved in thefacility with which the stroke sensor is inspected or replaced.

What is claimed is:
 1. A fluid pressure cylinder with a built-in strokesensor including a cylinder having a bottom member at one of its ends, atubular piston rod reciprocatively movable in said cylinder and having arod head at one of its ends, and said stroke sensor being constituted bya sensor body and a sensor rod provided in the cavity of said pistonrod, said fluid pressure cylinder with the stroke sensor beingcharacterized in that an eccentric member is attached to a first end ofsaid sensor rod, a recess/projection coaxial with said sensor rod isprovided at the center of said eccentric member, a projection/recessaxially supported by a recess/projection provided at the center of anend surface of said rod head is provided at an end of said eccentricmember, and a ring-like member engaging with said recess/projection ofsaid eccentric member is mounted in the cavity of said piston rod.
 2. Afluid pressure cylinder with a built-in stroke sensor including acylinder having a bottom member at one of its ends, a tubular piston rodreciprocatively movable in said cylinder and having a rod head at one ofits ends, and said stroke sensor being constituted by a sensor body anda sensor rod provided in the cavity of said piston rod, said fluidpressure cylinder with the stroke sensor being characterized in that aneccentric member is attached to an end of said sensor rod, arecess/projection coaxial with said sensor rod is provided at the centerof said eccentric member, a projection/recess axially supported by arecess/projection provided at the center of an end surface of saidbottom member is provided at an end of said eccentric member, and aring-like member engaging with said recess/projection of said eccentricmember is mounted in the cavity of said cylinder.
 3. A fluid pressurecylinder with a built-in stroke sensor including first and secondtubular members, each of said first and second tubular members having afirst end and a second end, said second tubular member being positionedwithin the cavity of said first tubular member with the first end ofsaid first tubular member being adjacent the first end of said secondtubular member, thereby forming an annular chamber between said firstand second tubular members, an annular member joining the first end ofsaid first tubular member to the first end of said second tubularmember, said annular member and the first end of each of said first andsecond tubular members forming the first end of the pressure cylinder, atubular piston rod having a first end and a second end with the firstend of the tubular piston rod being slidably positioned in the chamberbetween said first and second tubular members for reciprocating motiontherein and with the second end of the tubular piston rod extendingbeyond the second end of said second tubular member, said tubular pistonrod having a rod head at the second end of the tubular piston rod, afirst annular seal positioned between the outer surface of the tubularpiston rod and the inner surface of the first tubular member to formfirst and second power chambers between said tubular piston rod and theinner surface of said first tubular piston rod and the inner surface ofsaid first tubular member on either side of said first annular seal toreceive operating fluid therein to reciprocate said piston rod, a bottomend removably attached to the first end of the pressure cylinder, asensor accommodation tube positioned within the cavity of said secondtubular member, a sensor rod having a sensor body thereon positionedwithin said sensor accommodation tube to thereby form said built-instroke sensor, a first one of said sensor accommodation tube and saidsensor rod being secured to said bottom end, the second one of saidsensor accommodating tube and said sensor rod being secured to saidtubular piston rod adjacent the second end thereof, a second annularseal positioned between the tubular piston rod and the second tubularmember whereby said bottom end and said first one of said sensoraccommodation tube and said sensor rod can be removed for inspection ofthe stroke sensor without leakage of the operating fluid from the firstand second power chambers.
 4. A fluid pressure cylinder in accordancewith claim 3 wherein said second tubular member is positioned at leastsubstantially coaxially with said first tubular member.
 5. A fluidpressure cylinder in accordance with claim 4 wherein said tubular pistonrod is positioned at least substantially coaxially with said secondtubular member.
 6. A fluid pressure cylinder with a built-in strokesensor, comprising a first tubular member having a first end and asecond end, a bottom member connected to said first end of said firsttubular member, thereby forming a chamber within said first tubularmember, a tubular piston rod having a first end and a second end, thefirst end of said tubular piston rod being slidably positioned withinsaid chamber for reciprocating movement within said chamber, the secondend of said tubular piston rod extending beyond the second end of saidfirst tubular member, said tubular piston rod having a rod head at thesecond end of the tubular piston rod, a sensor rod having a sensor bodyeccentrically positioned thereon, said sensor rod and sensor body beingpositioned within the cavity of said tubular piston rod to thereby formsaid built-in stroke sensor, an eccentric member connected to one end ofsaid sensor rod, one of said eccentric member and said rod head havingan annular projection thereon with the other one of said eccentricmember and said rod head having an annular recess therein for receivingsaid annular projection, the one of said annular projection and saidannular recess which is part of said eccentric member being coaxial withrespect to said sensor rod, one of said eccentric member and said rodhead having a longitudinally extending projection thereon with the otherone of said eccentric member and said rod head having a longitudinallyextending recess therein for receiving said longitudinally extendingprojection, the one of said longitudinally extending projection and saidlongitudinally extending recess which is part of said rod head beingcoaxial with respect to said tubular piston rod, the one of saidlongitudinally extending projection and said longitudinally extendingrecess which is part of said eccentric member being eccentricallypositioned with respect to said sensor rod.
 7. A fluid pressure cylinderin accordance with claim 6 wherein the one of said annular projectionand said annular recess which is part of said rod head is coaxial withrespect to said tubular piston rod.
 8. A fluid pressure cylinder inaccordance with claim 7 wherein the longitudinally extending projectionand the longitudinally extending recess support said sensor rod andsensor body for rotation about the longitudinal axis of said tubularpiston rod.
 9. A fluid pressure cylinder in accordance with claim 8wherein the annular projection and the annular recess preventsignificant longitudinal movement of said sensor rod with respect tosaid tubular piston rod.
 10. A fluid pressure cylinder in accordancewith claim 9 wherein said annular recess is in said eccentric member,and wherein said longitudinally extending recess is in said rod head.11. A fluid pressure cylinder in accordance with claim 10 furthercomprising a sensor accommodation tube positioned within the cavity ofsaid tubular piston rod, with said sensor body being positioned withinthe cavity of said sensor accommodation tube.
 12. A fluid pressurecylinder in accordance with claim 9 wherein said annular recess is insaid eccentric member, and wherein said longitudinally extending recessis in said eccentric member.
 13. A fluid pressure cylinder in accordancewith claim 12 further comprising a sensor accommodation tube positionedwithin the cavity of said tubular piston rod, with said sensor bodybeing positioned within the cavity of said sensor accommodation tube.14. A fluid pressure cylinder in accordance with claim 9 wherein saidannular projection is on said eccentric member, and wherein saidlongitudinally extending recess is in said rod head.
 15. A fluidpressure cylinder in accordance with claim 14 further comprising asensor accommodation tube positioned within the cavity of said tubularpiston rod, with said sensor body being positioned within the cavity ofsaid sensor accommodation tube.
 16. A fluid pressure cylinder inaccordance with claim 9 wherein said annular projection is on saideccentric member, and wherein said longitudinally extending recess is insaid eccentric member.
 17. A fluid pressure cylinder in accordance withclaim 16 further comprising a sensor accommodation tube positionedwithin the cavity of said tubular piston rod, with said sensor bodybeing positioned within the cavity of said sensor accommodation tube.18. A fluid pressure cylinder with a built-in stroke sensor, comprisinga first tubular member having a first end and a second end, a bottommember connected to said first end of said first tubular member, therebyforming a chamber within said first tubular member, a tubular piston rodhaving a first end and a second end, the first end of said tubularpiston rod being slidably positioned within said chamber forreciprocating movement within said chamber, the second end of saidtubular piston rod extending beyond the second end of said first tubularmember, said tubular piston rod having a rod head at the second end ofthe tubular piston rod, a sensor rod having a sensor body eccentricallypositioned thereon, said sensor rod and sensor body being positionedwithin the cavity of said tubular piston rod to thereby form saidbuilt-in stroke sensor, an eccentric member connected to one end of saidsensor rod, one of said eccentric member and said bottom member havingan annular projection thereon with the other one of said eccentricmember and said bottom member having an annular recess therein forreceiving said annular projection, the one of said annular projectionand said annular recess which is part of said eccentric member beingcoaxial with respect to said sensor rod, one of said eccentric memberand said bottom member having a longitudinally extending projectionthereon with the other one of said eccentric member and said bottommember having a longitudinally extending recess therein for receivingsaid longitudinally extending projection, the one of said longitudinallyextending projecting and said longitudinally extending recess which ispart of said bottom member being coaxial with respect to said tubularpiston rod, the one of said longitudinally extending projection and saidlongitudinally extending recess which is part of said eccentric memberbeing eccentrically positioned with respect to said sensor rod.
 19. Afluid pressure cylinder in accordance with claim 18 wherein the one ofsaid annular projection and said annular recess which is part of saidbottom member is coaxial with respect to said tubular piston rod.
 20. Afluid pressure cylinder in accordance with claim 19 wherein thelongitudinally extending projection and the longitudinally extendingrecess support said sensor rod and sensor body for rotation about thelongitudinal axis of said tubular piston rod.
 21. A fluid pressurecylinder in accordance with claim 20 wherein the annular projection andthe annular recess prevent significant longitudinal movement of saidsensor rod with respect to said bottom member.
 22. A fluid pressurecylinder in accordance with claim 21 wherein said annular recess is insaid eccentric member, and wherein said longitudinally extending recessis in said bottom member.
 23. A fluid pressure cylinder in accordancewith claim 21 further comprising a sensor accommodation tube positionedwithin the cavity of said tubular piston rod, with said sensor bodybeing positioned within the cavity of said sensor accommodation tube.